One of the advantages of CORBA is that it is an open industry standard, not a proprietary technology from a single company. And one of the features of CORBA is that ORBs that are networked together should be able to interoperate. In other words, client programs should be able to access objects spread across multiple ORBs, even if the ORBs are from different vendors.
To make this work, the OMG has defined a "wire format" for remote-method-call messages. There are a few implementations of the wire-format standard, but the best known is IIOP, which stands for Internet Interoperability Protocol. IIOP lets you connect ORBs together via the TCP/IP networking protocol and allow them to work together. Since the Internet uses TCP/IP, you can write clients that access remote CORBA objects across the Internet.